How does it feel to be working while most people are sleeping? In the third of a series following those who drive Britain's 24-hour society through the small hours, we join rubbish collectors in central London.

"If you've got an open mind it's a brilliant metropolis," says Neil Hitchcock, checking the side view mirror as he drives a 15 tonne truck on the motorway.

He is referring to Europe's biggest city, London, where we are heading from Buckinghamshire on the M40.

Neil is not the first to feel this way. But he has an unusual perspective. He has spent more than two decades collecting rubbish, much of it at night.

"You see all sorts," he chortles. "You have to take everything in your stride." Mark Harries, his more subdued colleague, nods knowingly in the passenger seat.

Tonight the men, both long-time Biffa employees, are collecting waste from central London's restaurants, cafes and shops. The truck won't return to the High Wycombe depot until five o'clock in the morning when the noise curfew is lifted.

"This isn't a bad motor," Neil says fondly of the truck. "It's good in town. But on the motorway it rattles like a tin can."

Heading into London, we are going against the flow of evening traffic.

"This is one of the best benefits of night work," says Mark. "What can take an hour-and-a-half during the day can take 20 minutes at night."

City never stops

Passing through Acton we arrive in Kilburn. The first "job" is a chain of coffee shops explains Mark, reaching for thick gloves on the dashboard before getting out.

Neil climbs out more gingerly. "Arthritis" he announces, to explain a visibly shaky knee.

"Years of the same movement, I've had it since I was 30," he adds, before his voice is drowned by the truck's beeping alert sounding. Within minutes, Mark has thrown the blue bin bags into the back and a churning sound kicks in. Then both men are back in the front, and we are off to Oxford Street.

This is the time that annoys me - others are having fun and I've got work ahead

Neil Hitchcock, Biffa employee

Driving through Hanover Square, the height and breadth of the truck afford us an elevated view of the 18th Century buildings in the heart of Mayfair.

While Mark and Neil's work day is beginning, hordes of people are in post-work mood, chatting to friends or disappearing into the Tube.

"The West End never stops," says Neil, squeezing the vehicle through what looks like an unfeasibly small gap.

As we turn into Regent Street, pedestrians dash across the road, apparently oblivious to the looming truck as it negotiates bollards and parked cars. A cyclist pulls out.

Driving is one part of the job, but knowing the route is also crucial, especially in the centre.

You learn the journey by doing it night after night, says Mark, who is a regular on this route. "There's no point being on the right road if you face the wrong way, or can't park."

Rest stops

Coffee shop chains and smart clothes shops are closed for business, while pubs and bars fill up and couples enter restaurants.

"This is the time that annoys me - others are having fun and I've got work ahead," says Neil, as people spill out of theatres. Unlike some night work, which happens in seclusion, rubbish collection is public.

UK WASTE

Total UK landfill waste hit 335 million tonnes in 2004

Commerce produces 12% of total waste, households 12%.

The single biggest source of waste is construction and demolition

Current landfill tax is £24/tonne set to double to £48/tonne in 2010/11.

Source: DEFRA/LGA

But that comes with its own risks. The pair know to stay alert, to avoid the drunken punch ups that can erupt without warning. Mark was threatened only three weeks ago around two o'clock in the morning, behind Leicester Square.

But generally people are good humoured, adds Neil, the tireless optimist.

"It can be quite comical," he laughs. "One time this bloke came running out of the pub - in the buff."

Once the Tube has closed, requests for lifts home are not uncommon. Batting away such demands is often easier than the job in hand - getting access to the rubbish. Wheelie bins might be locked up or hard to reach.

But there is a strict timetable to be in certain places at certain times, or they risk being fined.

Then there are more prosaic difficulties - stopping for calls of nature, for example. "You can't just quickly park this truck and nip in somewhere," says Neil. "Where is open at 2am?"

The same goes for food. Twenty-four hour city it may be, but it's hard to get a nutritious meal in London in the small hours.

"I don't usually get hungry at night until I smell it," says Mark, of the whiff of fast food. Less than half an hour later he is tucking into a Kentucky Fried Chicken.

Stricter rules

With tougher rules about what can and cannot be sent to landfill, rubbish collectors need to know what they are putting in the back of their truck. Among the oddities left for them in the past was a new pair of Lacoste trainers worth £250. There is also "a lot of nicked stuff" - TVs, videos - not to mention mattresses.

"One time we kept filling up the back, but it never got full. Until we realised someone had binned most of a car engine. It had gone right through the floor of the truck. There was a huge gaping hole!" says Neil.

As we head out of London westwards, we pass other night workers doing road repairs. An ambulance hurtles past before we turn into an apparently deserted industrial estate: the dump.

Ahead, an enormous steaming pile of rubbish sits under a corrugated roof. A driver is pushing the waste into the corner in a forklift truck.

Spray smell

Leaving the truck, the stench is overwhelming. Beneath a sickly sweet smell is an undeniably rotten odour.

"If you think this is bad, imagine what its like without that to disguise it," says Neil, pointing to what looks like spray above the pile.

He reverses the truck before the rubbish tumbles out. The vehicle, weighed on arrival, typically up-ends 10-11 tonnes of waste by the end of a shift.

It is distinctly cooler and a light drizzle has set in. "When we pass the motorway the temperature drops by about two degrees" says Neil. "You really notice it in winter."

The buzz of London feels far away. Neil, who has been chirpy until this moment, sighs. "Its not natural working this late. It can mess with your head."

We are dropped off, but Mark and Neil embark on a final round. We need to cut our waste, says Neil, but someone still has to collect it.